A capacitance type sensor is used as a device for converting the intensity and direction of a force applied by an operator, into an electric signal. For example, as an input device for a game machine used is a device incorporated as a capacitance type force sensor, so-called joy stick, for inputting operations in multidimensional directions.
Using the capacitance type sensor, an operation quantity with a predetermined dynamic range can be input as the intensity of a force applied by the operator. Such a sensor may be used in the form of a two-dimensional or three-dimensional force sensor capable of detecting each directional component divided from the applied force. In particular, a capacitance type force sensor in which a capacitance element is made up of two electrodes and a force is detected on the basis of a change in the capacitance value due to a change in the interval between the electrodes, has a merit that a cost reduction can be intended by simplifying the construction. Therefore, sensors of this type have been put in practical use in various fields.
A capacitance type sensor is known that includes a pair of fixed electrodes for detecting opposite directional componential forces, and a displacement electrode disposed so as to be opposed to the pair of fixed electrodes. The capacitance type sensor detects an externally applied force on the basis of changes in the capacitance values of a capacitance element formed between one fixed electrode and the displacement electrode and a capacitance element formed between the other fixed electrode and the displacement electrode. The pair of fixed electrodes are supplied with signals, respectively. The signals are delayed on the basis of changes in the capacitance values of the respective capacitance elements, and then read by an exclusive OR circuit or the like to derive an output signal.
In the sensitivity characteristic of the above capacitance type sensor, however, each dimensional componential force may not sufficiently be detected. In addition, when the signals to be input to the respective fixed electrodes contain noises, the sensor may erroneously operate because an erroneous output signal is detected.
Therefore, a principal object of the present invention is to provide a capacitance type sensor superior in sensitivity characteristic and hard to be influenced by noise.